The Other Outer
Moons and AsteroidsMiranda
(left)
- a moon of Uranus and Gaspra (right) - a small asteroid

The
inner planets have no moons, but Mars has two tiny ones and both are thought
to be captured asteroids. The Gas and Ice Giant Planets each have
around 20 moon and, other than those already described, they are similar
in nature - rock and ice bodies in deep-freeze. Although some of
the larger moons, particularly around the Ice Giants, may display cold
volcanism as does Triton, none offers good habitats for life.
The asteroids must be considered to be in a similar situation, though
they receive more sunlight than the distant moons and it is known that
some contain interesting chemicals associated with the precursors of life.